Phase shifting circuit



Jan. 21, 1941. 5, w RM 2,229,450

PHASE SHIFTING CIRCUIT Original Filed Dec. 14, 1937 Hgl.

Inventor: George W. Sara-nan,

y n; axlwlm is Atcorney.

Patented Jan. 21, 1941 PATENT OFFICE PHASE SHIFTING CIRCUIT George W. Garman, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Original application December 14, 1937, Serial No. 179,710. Divided and this application June 15,

1940, Serial No. 340,758

5 Claims.

My invention relates to electric circuits and more particularly to electric circuits {or shifting the phase of an alternating potential derived from a source with respect to the potential of that source.

This applica tion is a division of my copending patent application Serial No. 1791 10, filed December 14, 1937, and which is assigned to the assignee of this application.

My invention is of general application in electric control and regulating systems, although it is particularly adapted for use in connection with electric power converting apparatus for transmitting energy between direct current and alternating current systems, or between alternating current systems, by the use of electric valves. In such applications it is customary to control the transmission of power between the direct current and the alternating current systems, or between alternating current systems, by shifting the phase of the potentials applied to the control members or grids of the electric valves with respect to the applied anode-cathode potentials. Various arrangements have been provided heretofore to effact this phase shift of the grid potential. Static phase shifters, that is, electric circuits including various combinations of resistance, inductance and capacitance, have proved to be most satisfactory from the standpoint of simplicity, economy and reliability. In view of the peculiar adaptability of phase shifting circuits of the static type, there has been evident a decided need for improved circuits of this nature which are simple in construction and arrangement and which employ a minimum number of impedance elements.

It is an object of my invention to provide a new and improved electric circuit. It is another object of my invention to provide a new and improved electric phase shifting circuit of the static impedance type.

It is a further object of my invention to provide a new and improved static impedance phase shifting circuit for controlling electric power converting apparatus.

Briefly stated in an illustrated embodiment of :my invention, I provide a phase shifting circuit of the static impedance type which comprises an electric network of the bridge type in which opposite arms are of the reactive type and in which other opposite arms are of the resistive type. The reactive branches of the network may be inductances or capacitances. One pair of opposite junctures of the reactive elements and the resistances is connected to terminal connections of a winding which is energized from an alternating current circuit, and the other pair of opposite junctures of the reactive elements and the resistances are connected to a resistance of a. voltage divider. The resistance of the voltage divider is provided with an intermediate point which is connected to one of the terminal connections of the winding, and the resistance of the voltage divider is each provided with a movable or adjustable contact member in operative relation with the resistance. An output circuit is connected to an intermediate connection of the winding and the movable contact member of the voltage divider.

For a better understanding of my invention, reference may be had to the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims. Fig. l diagrammatically illustrates an embodiment of my invention as applied to an electric valve power converting system and Fig. 2 represents certain operating characteristics thereof. Figs. 3, 4, and 5 diagrammatically illustrate further modifications of my invention.

Fig. 1 of my invention is diagrammatically i1- lustrated as applied to an electric valve power converting system for transmitting energy between an alternating current circuit l and a direct current circuit 2 through a transformer 3 and electric valve means 4 and 5. Electric valve means 4 and 5 are preferably of the type employing an ionizable medium, such as a gas or a vapor, and each includes an anode 6, a cathode 1 and a control member or grid 8 which controls the conductivity of the electric valve.

I provide a phase shifting circuit 9 of the static impedance type, which includes a winding III which is energized from the alternating current circuit I. Winding I0 is provided with connections II and I2 and a connection I3 which is electrically intermediate the connections II and I2. While for the purposes of illustration I have shown the connections I l and I2 as being located intermediate the ends of the winding I0, it is to be understood that these connections may be located at the ends of the winding and may be considered as terminal connections. A pair of electric paths is connected to one of the terminal connections, as for example connection l2; one of the paths includes a capacitance H and the other path includes an inductance IS. A voltage divider I6 is interposed between the pair of electric paths and'the connection II- and includes a resistance element ll having terminal connections l8 and I9. Terminal connection I8 is connected to capacitance l4, and terminal connection i9 is connected to inductance 85. Resistance i! is also provided with an intermediate point or connection 20 which is connected to connection ii of winding i0. An adjustable or movable contact member 29 is provided in operative relation with resistance H. An output circuit 22 is connected across the intermediate connection 83 and the movable contact 2i of the voltage divider i6. Resistance H; capacitance id and inductance i5 maybe proportioned to determine the range of phase shift. By the proper proportioning of these elements, the voltage of circuit 22 may be varied in phase through regions of very small angular displacement to substantially 360 electrical degrees. The range of phase shift obtained is increased by increasing the value of the resistance ill relative to the ohmic values of the capacitance i l and inductance i5.

Excitation circuits 2-3 and 24 are associated with electric valve means t and 5, respectively, and impress on the associated control members 2 periodic or alternating voltages which control thr conductivities of the electric valves. Each of the excitation circuits 2.? and 2% may include means such as a saturable inductive device 25 which produces an alternating voltage of peaked wave form. Each of the saturable inductive devices 25 includes a core member 28 having a shunt magnetic path 2?, a restricted saturable portion 28, a primary winding 29 which is connected to circuit 22, and a secondary winding 30 which is associated with the restricted saturable portion 28 and which produces an alternating voltage of peaked wave form. Any suitable means such as a battery 3i may be employed to impress on the associated control member 8 a negative unidirectional biasing potential, and a current limiting resistance 32 may be connected in series .relation with the associated control member.

The operation of the embodiment of my invention shown in Fig. 1 will be explained by considering the electric valve system when-power is being transmitted from the alternating current circuit i to the direct current circuit 2 through transformer 3 and electric valve means 5 and 5. It is well understood by those skilled in. the art that the average voltage impressed on circuit 2 is maximum when there is substantial phase coincidence between the voltages impressed on the control members 8 relative to the applied anodecathode voltage. That is, the voltage impressed on circuit 2 is maximum when the electric valve means t and 5 are rendered conductive at the beginning of the positive half cycles of applied anode-cathode voltage. When the load connected to circuit 2 is inductive, the average voltage impressed thereon will be minimum when the electric valves are rendered conductive at substantially the 90 lagging position with respect to the anode-cathode voltage. Of course, the average voltage impressed on circuit 2 will assume corresponding values for intermediate phase relationships between the voltages impressed on the control members 8 and the voltages applied between the anodes and cathodes of the electric valves.

The phase of the'voltage impressed on circuit 22 and hence the phase of the voltage impressed on control members 2 of electric valves Q and 5 is controllable by operation of the movable contact member'2l of the voltage divider 96 in phase shifting circuit 9. For example, if it is desired to effect a progressive advancement in phase of thealternating voltage of peaked wave form impressed on control members 8 of electric valves 4 and 5, the movable contact member 2| is initially placed in engagement with terminal l8 or resistance l1 and is moved in a counterclockwise direction. The alternating voltage impressed on the output circuit 22 is progressively advanced in phase with respect to the alternating voltage of circuit I or with respect to the alternating voltage applied to winding Ill. The range of phase shift for such operation of the movable contact member 2! is determined by the relative ohmic values of resistance i1, capacitance i4 and inductance it.

For a more complete explanation of the manher in which the phase shifting circuit 9 operates, reference may be had to the operating characteristics shown in Fig. 2. For a particular set of values for resistance ll, capacitance M and inductance E5, the vector AB represents the voltage appearing between terminals H and E2 of winding it and the vector CB represents the voltage appearing across the terminals of the capacitance it. The vector AC represents the voltage appearing across that portion of the resistance i! of voltage divider it which lies between the intermediate point 20 and the terminal l8. Vector DB represents the voltage appearing across the terminals of inductance i5 and vector AD represents the voltage appearing across the terminals of the portion of resistance l1 lying between the the intermediate point 20 and terminal E9. The point 0 represents the potential of the intermediate connection fl3 of winding E0, The vector 00 represents the voltage impressed on the output circuit 22. When the movable contact memher 25 is in engagement with the terminal I8 of resistance t1, the voltage impressed on the output circuit 22 has a phase position corresponding to the position of vector 00. As the movable contact member 26 is rotated in a counterclockwise direction, the vector OC assumes the positions OE, OF and 0G. When the movable contact member 2! is in engagement with the intermediate point 20 of resistance H, the vector representing the voltage impressed on circuit 22 coincides with the vector 0A. For progressive member 2i engages terminal H of resistance i'lv the voltage vector of circuit 22 coincides with the vector OD. It will be noted that for the particular vector diagram shown, the phase of the voltage impressed on circuit 22 has been varied through substantially 180 electrical degrees. Of course, it is to be understood that the range of phase may be increased or decreased by the proper choice of values for resistance l1, capacitance I4 and inductance i5. For example, by increasing the value of the resistance 51 so that the vector diagram of the phase shifting circuit includes the triangles ALB and AMB, the output voltage may be rotated counterclockwise from the position OL to the position OM, and the voltage impressed on circuit 22 may be varied in phase from the position indicated by vector 0L to the position 'of vector OM, which is a range substantially in excess of 180 electrical degrees.

In Fig. '3 of the accompanying drawing there is illustrated a modification of the embodiment of my invention shown in Fig. 1, and corresponding elements have been assigned like reference numerals. To control the range of phase shift of the voltage impressed on output circuit 22, I provide a pair of movable impedance elements, such as adjustable resistances 33 and 34, which are connected between the pairs of electric circuits and the terminal connection ll of winding Ill. The adjustable resistances 33 and 34 serve as an agency for controlling the maximum range of phase shift occasioned by moving the contact member 2| over the resistance H.

The operation of the embodiment of my invention shown in Fig. 3 is substantially the same as that explained above in connection with the arrangement of Fig. l. The resistances 33 and 34 may be adjusted to establish the range of phase shift available. As the effective values of the resistances 33 and 34 are increased, the range of phase shift is also increased.

Fig. 4 diagrammatically illustrates another embodiment of my invention in'which a static phase shifting circuit of the bridge type is employed. A bridge network 35 includes opposite branches comprising reactive impedance elements, such as capacitances 36 and 31, and opposite resistive branches include resistances 38 and 39. One pair of opposite junctures of the resistances and capacitances, such as junctures 40 and 4|, are connected to terminal connections ii and l2 of winding l0, and the other pair of junctures 42 and 43 are connected to terminals I8 and |9 of the resistance ll of the voltage divider I6. The intermediate point 20 of the resistance I1 is connected to juncture 4| and terminal connection l2 of winding Ill.

The phase of the alternating voltage impressed on circuit 22 may be progressively advanced by moving the contact member 2| from the terminal l8 of resistance I! to the terminal IQ of this resistance. This arrangement permits smooth and continuous control of the phase of the output voltage over ranges extending from substantially 360 to very small angular displacements.

In Fig. 5 there is diagrammatically illustrated another embodiment of my invention which is similar in many respects to that shown in Fig. 4. The arrangement in Fig. 5 is particularly adaptable for shifting the phase of the voltage of circuit 22 within a region or range of substantially 360 electrical degrees. A voltage divider 44 may be provided with a continuous or closed resistance 45 which is connected to the bridge circuit 35 and the winding l0. Terminal connections 46 of resistance 45 are connected to juncture 43 of the bridge 35 and to terminal I l of winding l0. Point 41 is connected to juncture 40 of bridge 35; point 48 is connected to juncture 42 and to terminal l2 of winding I0; and point 49 is connected to juncture 4|. A movable contact means or contact member 50 is operatively associated with resistance 45 and serves to shift the phase of the voltage impressed on output circuit 22 which is connected between the movable contact 50 and intermediate connection I 3 of winding Ill. The contact member 50 may be moved over substantially'the entirety of resistance 45.

By rotating the contact 50 of the voltage divider 44, the voltage impressed on circuit 22 may be progressively advanced or rearded in phase throughout a 369 electrical degree range. The shift in phase of the voltage of circuit 22 is continuous and smooth throughout this range.

vWhile I have shown and described my invention 'as applied to a particular system of connections and as embodying various devices diagrammatically shown, it will be obvious to those skilled in the art that changesand modifications may be made without departing from my invention and I therefore aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In combination, an alternating current circuit, apparatus for producing a periodic voltage variable in phase with respect to the voltage of said circuit and including a winding having a pair of connections and a connection electrically intermediate said pair of connections, a bridge circuit connected to said pair of connections and having reactive and resistive branches and a voltage divider connected across said bridge circuit, and an output circuit connected between the intermediate connection and said voltage divider.

2. In combination, an alternating current circuit, apparatus for producing an alternating voltage variable in phase with respect to the voltage of said circuit and including a winding having a pair of terminal connections and a connection electrically intermediate said terminal connections, a bridge circuit connected to said terminal connections and comprising a pair of opposite reactive branches and a pair of resistive branches and a voltage divider including a resistance having points connected to juncture of said resistive and reactive branches of said bridge circuit, and an output circuit connected between the intermediate connection and said voltage divider.

3. In combination, an alternating current circuit, apparatus for producing a periodic voltage variable in phase with respect to the voltage of said circuit and including a winding having a pair of connections and a connection intermediate said pair of connections, a bridge circuit con nected to said pair of connections and having reactive and resistive branches and a voltage divider connected across said bridge circuit, said voltage divider being provided 'with adjustable contact means, and an output circuit connected between the intermediate connection and said contact means.

4. In combination, an alternating current circuit, apparatus for producing an alternating voltage variable in phase with respect to the voltage of said circuit and including a winding having a pair of connections and a connection electrically intermediate said pair of connections, a bridge circuit connected to said pair of connections and comprising reactive and resistive branches and a voltage divider connected across said bridge circuit, said voltage divider comprising a closed resistance and contact means for engaging said resistance throughout substantially its entirety, and an output circuit connected between the intermediate connection and said contact means.

5. In combination, an alternating current circuit, apparatus for producing an alternating voltage variable in phase with respect to the voltage of said circuit and including a winding having a pair of terminal connections and a connection electrically intermediate said terminal connections, a bridge circuit connected to said terminal connections and comprising a pair of reactive branches and a pair of resistive branches and a voltage divider including a resistance having points connected to the junctures of said resistive and reactive branches of said bridge circuit, said 

